Erdos Number

May 4, 2012

My colleague impressed me when I knew his Erdos number is 5. And that his mathematical genealogy tree goes all the way to Euler. Leonard Euler (1707-1783), a legendary mathematician, published over 800 papers in his lifetime. His name went into so many areas of mathematics, it’s difficult not to encounter him if one does enough math. For a long time, nobody is more prolific than him, until Paul Erdos (26 March 1913 – 20 September 1996) came along.

According to Divison by Zero on a article called “Publish or Perish”, three quarters of all mathematicians published five or fewer papers. Either it’s really hard to publish papers or most institutions have paper requirement that are not harsh. Our institution requires that our tenure-track people publish at least 6 papers to get their tenure.

So, anyway, to be connected to Euler, is an honour. This colleague’s advisor is an Egyptian, whose advisor is also Egyptian and so on and so forth and somewhere after 9 or 10 names, you’ll see names of legendary mathematicians, and then Euler’s name will appear.
I forgot to say that his Erdos number is 4. Erdos has 1525 mathematical papers written. He published with so many people in his lifetime, there’s something called the Erdos number. If you’ve published a paper with Erdős, your Erdős number is 1. If you’ve co-authored a paper with someone whose Erdős number is 1, then your Erdős number is 2, so on and so forth. (Interestingly, mathematicians also created a Bacon number using the same way of counting about acting with Kevin Bacon.) Most Physics/Chemistry/Economics Nobel laureates and Field Medalists have low Erdos numbers. (See the list maintained by Oakland University here.)

Being inspired by my colleague, I also went on a journey to find out if I’m mathematically related to some famous mathematicians. After all, my advisor is a Briton who had his PhD from Oxford even though he is now permanently “stationed” in Tokyo. So I went on that Math Genealogy webpage and started searching for advisor’s advisor’s advisor, etc one step at a time. To my surprise, I came across Issac Newton. I also looked at other branches of the genealogy tree and was more proud to be mathematically related to Michael Atiyah.

I went on next to find out my Erdos number. And my first step was to look for my advisor’s Erdos number. That was not hard to do, as he published a lot. It turned out that his Erdos number is 4,and since I’ve one paper with him, that makes me a 5! For quite a while, I was very happy with that (not that it means anything or I’ve accomplished anything). Then I realize maybe I should look at the Erdos number of other people I’ve collaborated with. And then I found out that James Sellers has an Erdos number of a very low TWO!